Packaging machines are known in which the articles to be packaged, for example, cans or bottles, are directed along lanes between spaced guide rails toward cartons or other types of containers. The lanes are oriented at an angle to the path of travel of a plurality of spaced selectors, and at the location where the lanes and the path of travel of the selectors intersect, the selectors are forced between successive articles, causing a predetermined number of articles to be grouped in a desired configuration between successive selectors. As the selectors progress along their path of travel, the groups of articles are inserted into containers, which are transported in timed relation with the pockets between the selectors. Machines which operate in this manner are disclosed, for example, in U.S. Pat. No. 4,887,414 to Arena, and U.S. Pat. No. 5,546,734 to Moncrief et al., the entire disclosures of which are incorporated hereinto by reference.
While continuous motion packaging machines of the type described are effective in permitting high speed article packaging of articles into containers in a single layer, they may not be as effective when the articles are to be packaged in more than one layer in a stacked configuration. When stacks of articles pass along the lanes between the guide rails, the selectors, which are located underneath the guide rails, generally will only engage the bottom article of each of the moving stacks of articles. The upper articles in the stack, being under pressure from the following stacks, will tend to keep moving and, not being constrained by engagement with the selector, may move out of alignment with the bottom article of the stack and/or each other. This disrupts the feeding of the stacks into a container, and may require slowing down the operation of the machine, or, in an extreme case, stopping the machine if a jam occurs.